/*
 * Copyright (C) 2002  Terence M. Welsh
 * Ported to Linux by Tugrul Galatali <tugrul@galatali.com>
 *
 * Rgbhsl is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as 
 * published by the Free Software Foundation.
 *
 * Rgbhsl is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "rgbhsl.h"

void rgb2hsl (float r, float g, float b, float *h, float *s, float *l)
{
	int huezone = 0;
	float rr, gg, bb;

	/*
	 * find huezone 
	 */
	if (r >= g) {
		huezone = 0;
		if (b > r)
			huezone = 4;
		else {
			if (b > g)
				huezone = 5;
		}
	} else {
		huezone = 1;
		if (b > g)
			huezone = 2;
		else {
			if (b > r)
				huezone = 3;
		}
	}

	/*
	 * luminosity 
	 */
	switch (huezone) {
	case 0:
	case 5:
		*l = r;
		rr = 1.0f;
		gg = g / *l;
		bb = b / *l;
		break;
	case 1:
	case 2:
		*l = g;
		gg = 1.0f;
		rr = r / *l;
		bb = b / *l;
		break;
	default:
		*l = b;
		bb = 1.0f;
		rr = r / *l;
		gg = g / *l;
	}
	if (*l == 0.0) {
		*h = 0.0;
		*s = 1.0;
		return;
	}

	/*
	 * saturation 
	 */
	switch (huezone) {
	case 0:
	case 1:
		*s = 1.0f - b;
		bb = 0.0f;
		rr = 1.0f - ((1.0f - rr) / *s);
		gg = 1.0f - ((1.0f - gg) / *s);
		break;
	case 2:
	case 3:
		*s = 1.0f - r;
		rr = 0.0f;
		gg = 1.0f - ((1.0f - gg) / *s);
		bb = 1.0f - ((1.0f - bb) / *s);
		break;
	default:
		*s = 1.0f - g;
		gg = 0.0f;
		rr = 1.0f - ((1.0f - rr) / *s);
		bb = 1.0f - ((1.0f - bb) / *s);
	}

	/*
	 * hue 
	 */
	switch (huezone) {
	case 0:
		*h = g / 6.0f;
		break;
	case 1:
		*h = ((1.0f - r) / 6.0f) + 0.166667f;
		break;
	case 2:
		*h = (b / 6.0f) + 0.333333f;
		break;
	case 3:
		*h = ((1.0f - g) / 6.0f) + 0.5f;
		break;
	case 4:
		*h = (r / 6.0f) + 0.666667f;
		break;
	default:
		*h = ((1.0f - b) / 6.0f) + 0.833333f;
	}
}

void hsl2rgb (float h, float s, float l, float *r, float *g, float *b)
{
	/*
	 * hue influence 
	 */
	if (h < 0.166667) {	/* full red, some green */
		*r = 1.0;
		*g = h * 6.0f;
		*b = 0.0;
	} else {
		if (h < 0.5) {	/* full green */
			*g = 1.0;
			if (h < 0.333333) {	/* some red */
				*r = 1.0f - ((h - 0.166667f) * 6.0f);
				*b = 0.0;
			} else {	/* some blue */
				*b = (h - 0.333333f) * 6.0f;
				*r = 0.0;
			}
		} else {
			if (h < 0.833333) {	/* full blue */
				*b = 1.0;
				if (h < 0.666667) {	/* some green */
					*g = 1.0f - ((h - 0.5f) * 6.0f);
					*r = 0.0;
				} else {	/* some red */
					*r = (h - 0.666667f) * 6.0f;
					*g = 0.0;
				}
			} else {	/* full red, some blue */
				*r = 1.0;
				*b = 1.0f - ((h - 0.833333f) * 6.0f);
				*g = 0.0;
			}
		}
	}

	/*
	 * saturation influence 
	 */
	*r = 1.0f - (s * (1.0f - *r));
	*g = 1.0f - (s * (1.0f - *g));
	*b = 1.0f - (s * (1.0f - *b));

	/*
	 * luminosity influence 
	 */
	*r *= l;
	*g *= l;
	*b *= l;
}

void hslTween (float h1, float s1, float l1, float h2, float s2, float l2, float tween, int direction, float *outh, float *outs, float *outl)
{
	/*
	 * hue 
	 */
	if (!direction) {	/* forward around color wheel */
		if (h2 >= h1)
			*outh = h1 + (tween * (h2 - h1));
		else {
			*outh = h1 + (tween * (1.0f - (h1 - h2)));
			if (*outh > 1.0)
				*outh -= 1.0;
		}
	} else {		/* backward around color wheel */
		if (h1 >= h2)
			*outh = h1 - (tween * (h1 - h2));
		else {
			*outh = h1 - (tween * (1.0f - (h2 - h1)));
			if (*outh < 0.0)
				*outh += 1.0;
		}
	}

	/*
	 * saturation 
	 */
	*outs = s1 + (tween * (s2 - s1));

	/*
	 * luminosity 
	 */
	*outl = l1 + (tween * (l2 - l1));
}

void rgbTween (float r1, float g1, float b1, float r2, float g2, float b2, float tween, int direction, float *outr, float *outg, float *outb)
{
	float h1, s1, l1, h2, s2, l2, outh, outs, outl;

	rgb2hsl (r1, g1, b1, &h1, &s1, &l1);
	rgb2hsl (r2, g2, b2, &h2, &s2, &l2);
	hslTween (h1, s1, l1, h2, s2, l2, tween, direction, &outh, &outs, &outl);
	hsl2rgb (outh, outs, outl, outr, outg, outb);
}
